This invention relates generally to air conditioning systems and, more particularly, to a method and apparatus for reducing liquid carry over from an evaporator.
In a refrigeration circuit, wherein refrigerant vapor passes from the evaporator to the compressor, to the extent that the refrigerant isn""t completely evaporated, liquid refrigerant may be passed on to the compressor as liquid carry over, which affects both the performance and the life of the compressor.
There are generally two types of evaporator applications in which liquid carry over is a particular problem: flooded evaporators and falling film evaporators. In a flooded evaporator, wherein liquid refrigerant is introduced in the lower part of the evaporator shell, liquid droplets tend to be entrained in the refrigerant vapor flow leaving at the top of the heat exchanger tube bank. Similarly, in a falling film evaporator arrangement, wherein two phase refrigerant is introduced at the top of the tube bank, there tends to be a significant amount of liquid refrigerant that is entrained into the compressor suction.
One approach to solving this problem is to provide a liquid/vapor separator, either internally or externally of the evaporator. While these are effective, they add substantial expense to the system.
Another approach has been to provide sufficient vertical space between the top of the tube bank and the suction nozzle at the top of the shell such that droplets will be caused to flow downwardly by the force of gravity before they reach the suction nozzle. This, of course, requires the use of a larger shell, which in turn is costly because of the added materials and space that it occupies.
Yet another approach has been to provide a so called xe2x80x9celiminatorxe2x80x9d in the form of a wire mesh, between the top of the tube bank and the compressor suction. Such an eliminator tends to interrupt the flow of the liquid droplets, allowing them to collect on the eliminator and to eventually fall by the force of gravity. This approach is somewhat effective in controlling liquid carry over and, while it requires less space then the approach described hereinabove, it does require some additional space for the eliminator and also involves the cost of the eliminator. Further it is recognized as being passive in the sense that it simply turns back the droplets which, again, will tend to be entrained in the flow of refrigerant vapor as before.
In addition to the commonly used flooded evaporator and falling film evaporator applications discussed hereinabove, the present invention may be applicable to increase the system efficiency such that other applications become feasible. For example, in air conditioning systems in which the refrigerant is driven by reciprocating or scroll compressors, direct expansion evaporators, rather then flooded evaporators, are used because flooded evaporators do not provide sufficient suction super heat for use with such compressors. However, the use of flooded evaporators would be preferred if this problem can be overcome.
It is therefore an object of the present invention to provide an improved evaporator arrangement for reducing liquid carry over.
Another object of the present invention is the provision in an evaporator for effectively using the space within the evaporator shell.
Yet another object of the present invention is the provision for using a flooded evaporator in a system with reciprocating or scroll compressors.
Still another object of the present invention is the provision for an evaporator that is efficient and effective in use.
These objects and other features and advantages become more readily apparent in reference to the following description when taken in conjunction with the appended drawings.
Briefly, in accordance with one aspect to the invention, a baffle is located above the tube banks for interrupting the upward flow of liquid refrigerant droplets that would otherwise tend to flow to the compressor along with the refrigerant vapor. Heat is added to the baffle to cause an evaporation of the liquid droplets such that the resulting vapor passes to the compressor.
In accordance with another aspect of the invention, the baffle structure comprises a heat exchange having a fluid flowing therethrough, with a temperature of the fluid being warmer that the refrigerant such that sufficient heat is transferred to the refrigerant droplets to bring about the desired vaporization.
By yet another aspect of the invention, the fluid passing through the baffle heat exchanger can be warm water diverted from the entering the first pass of the cooler or it may be liquid refrigerant leaving the condenser before entering the expansion device.
In the drawings it is hereinafter described, a preferred embodiment is depicted; however, various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention.